Manufacturers of fiberglass containing products continue the search for commercially acceptable substitutes to traditional, formaldehyde-containing binder compositions. Health concerns about the irritant, allergenic, and possibly carcinogenic effects of off-gassing formaldehyde from of traditional phenol-formaldehyde and urea-formaldehyde binders in articles a diverse as building insulation, furniture upholstery, and textiles have prompted the industry to search for formaldehyde-free alternatives. However, presently available alternatives have their own challenges in terms of ease of manufacture, process emission, flame resistance, moisture resistance, sustainability, and cost, among other challenges.
One class of formaldehyde-free binder compositions relies on esterification reactions between carboxylic acid groups in polycarboxy polymers and hydroxyl groups in alcohols. Water is the main byproduct of these covalently crosslinked esters, which makes these binders more environmentally benign, as compared to traditional formaldehyde-based binders. However, these formaldehyde-free binder compositions also make extensive use of non-renewable, petroleum-based ingredients. Thus, there is a need for formaldehyde-free binder compositions that rely less on petroleum-based ingredients.
There are also formaldehyde-free binder formulations based on renewable carbohydrates, such as reducing sugars. These binders contain significant amount of renewable raw materials; therefore are more sustainable than petroleum-based binders. Unfortunately, these sugar-based binders generate high VOC (volatile organic compound) emissions during thermal curing. The high VOC emission of these binders limits their uses in applications such as fiberglass insulation, due to the ever-tightening emission permit limits in manufacturing facilities. Therefore, there is a need for sustainable formaldehyde-free binder compositions that emit low VOC emissions during thermal curing.
As an abundant and renewable material, protein has great potential to be an alternative to petroleum-based binders. Proteins are already used extensively as a component of adhesives for various substrates. However, many types of protein-containing adhesives have poor gluing strength and water resistance. Thus, there is a need to improve the bonding strength and water resistance of protein-containing binder compositions to levels that are similar to or better than those of conventional, petroleum-based binder compositions. These and other issues are addressed in the present Application.